The invention relates to a control device of a hydraulic system, used in particular for controlling a transmission of a motor vehicle.
Continuously variable transmissions have become known, e.g., from DE 195 44 644. They are equipped with hydraulically controlled actuating members for setting the transmission ratio and for providing a secure compressive grip on a chain belt between the conical disks.
The actuating members are controlled by means of valves that are arranged in a valve housing as known, e.g., from DE 196 46 447. The valves are controlled by means of an electronic control circuit arranged in an electronic control unit. The electronic system is composed of an electronic control portion with electronic components such as computer chips or integrated circuits and an electronic power portion with power semiconductors for controlling the valves. Because of the actuating current required in some cases for the control of solenoid valves, a significant amount of heat is generated in the electronic control unit. As a result, there can be heat failures of at least individual components, depending on the temperature level of each component, whereby the reliable operation of the entire control device is put at risk.
It is therefore the object of the present invention to improve the cooling of the electronic control unit and thereby provide a control device that works more reliably.
To meet this objective, the invention provides a control device with a hydraulic control unit and an electronic control unit, in particular for controlling a continuously variable cone-pulley transmission, with at least one valve arranged in a hydraulic control unit housing and with electronic components arranged in an electronic control unit housing. According to the invention, the hydraulic control unit and the electronic control unit are connected as one modular unit, and the aforementioned object of the invention is met by providing a holding volume for hydraulic fluid between the housing of the hydraulic control unit and the housing of the electronic control unit.
The holding volume or receptacle that is formed in this manner can receive, e.g., leakage fluid flowing from the hydraulic valves or the valve pistons of the hydraulic control unit. The holding volume is thereby filled with hydraulic fluid, which is more effective than air in carrying the heat away from the housing of the electronic control unit. Because the continuous supply of new leakage fluid during operation keeps the holding volume filled to overflow, the fluid that has been heated up by the electronic control unit is continuously transported away, resulting in improved cooling of the electronic control unit.
It is particularly advantageous if the holding volume is formed by a wall of the housing of the hydraulic control unit and a wall of the housing of the electronic control unit and in certain cases by at least one ridge.
In a particularly advantageous arrangement, the at least one ridge is part of the housing of the hydraulic control unit and/or the electronic control unit. It is also possible that the at least one ridge is interposed as a component between the respective walls of the two housings.
It is practical if the holding volume is open on one side, preferably at the top, to allow the heated fluid to run off and the newly arriving fluid to be taken in.
As a particularly advantageous feature, the holding volume is closed off by a seal between the housing of the hydraulic control unit and the housing of the electronic control unit or in the area of the ridge. This is of practical benefit in an embodiment of the invention, because it prevents an undefined outflow of fluid.
In another practical embodiment of the invention, it is especially practical if the surfaces where the housing of the hydraulic control unit and the housing of the electronic control unit and/or the ridge fit together are made fluid-tight to the farthest extent without the addition of a seal.
It is of particular advantage if the hydraulic control unit and the electronic control unit are screwed together so as to connect the two housings in a manner whereby the holding volume is essentially sealed in the area of the ridge.
The novel features that are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.